Research And Development Of Transmission Hydraulic Shift System For Power Shift

The application of power shift on tractors can reduce the workload of drivers,improve the competitiveness of tractor manufacturing companies,and promote the development of Agricultural Mechanization in China.Taking TG1804 tractor as the study object,this thesis solves the problem of shifting difficulty in the main gearbox when shifting,and designs a set of power shift system,which is applied to the tractor.In the real tractor experiments,there exists problems of shift failure and the fork shaft can't accurately back to the neutral.So the thesis puts forward an application combining FUZZY control and PID control,achieves precise control of the fork shaft position by controlling the displacement of the hydraulic cylinder piston rod.This thesis mainly carried out the following theoretical research and experimental work:The thesis puts forward the dynamic analysis of the shifting process considering the fork shaft can't back to the neutral accurately.Considering the requirements for synchronous time when dynamic shift,proposes a shift force determination method of combining static and dynamic shift.Establishes dynamic model of the fork shaft when static shift,determines synchronous force of synchronizer when dynamic shift.Finally,the relationship between the shifting force and the displacement of the fork shaft is obtained.The operation process of the power shift system is studied and the design of the electronic control system is completed.According to the basic parameters of the tractor,the hydraulic system components are selected by quantitative analysis,the hydraulic schematic diagram is drawn and the hydraulic system of the power shift system is designed.The reverse modeling,solid building and virtual assembly of the CATIA are used to complete the three-dimensional model of the vehicle transmission.On this basis,the power shift actuator is designed.Through the analysis of the rationality of the design,processing and installation of the mechanical parts,the optimization of the mechanical parts is designed.Finally,a set of reasonable power shift system is designed.Taking the hydraulic transmission system as the object,the thesis establishes the dynamic model of the valve controlling hydraulic cylinder.Hydraulic transmission system is proved stable through simulation.Designs the fuzzy controller and PID controller,builds the position control simulation model of piston rod,does the simulation when the viscosity damping coefficient of the hydraulic oil and the friction of the shifting mechanism is changed,the simulation result shows the model is stable.Finally through the bench test,the simulation model is proved to be stable.The result of the study shows that the position control simulation model can satisfy the stability of the fork shaft back to the neutral.The reliability of the model is verified through the real tractor test.The maximum response time of the fork shaft back to the middle position in the real tractor test is 0.168 seconds,which meets the designed requirement time 0.2 seconds.